Evaluation of PBRM1, PD-L1, CD31, and CD4/CD8 ratio as a predictive signature of response to VEGFR-TKI–based therapy in patients with metastatic renal cell carcinoma (mRCC) with IMDC intermediate prognosis: Results from the APAChE-I Study.
Authors: Chiara Ciccarese, Sebastiano Buti, Michela Roberto, Fabio Calabro, Cristina Masini, Francesco Massari, Maria Antonella Cannella, Giulia Mazzaschi, Serena Astore, Stefania Di Girolamo, Martina Panebianco, Veronica Mollica, Alessia Granitto, Vincenzo Fiorentino, Francesco Pierconti, Maurizio Martini, Camillo Porta, Giampaolo Tortora, Roberto Iacovelli
Journal: Journal of Clinical Oncology (2023)

714 Background: Intermediate IMDC group is the largest and most heterogeneous group of mRCC. Current first-line (1L) therapy options for these patients (pts) are based on either an anti-angiogenic agent (VEGFR-TKI) combined with immunotherapy (IO), or a combo of IO (ipilimumab+nivolumab [I/N]). No biomarkers (BM) for selecting the most effective regimen have been identified so far. Methods: Immunohistochemical expression of PBRM1, PD-L1, CD31, and CD4/CD8 ratio was evaluated on histological samples of intermediate-risk mRCC pts treated with VEGFR-TKI monotherapy, and then in pts receiving a VEGFR-TKI-based therapy or the immune doublet I/N. PBRM1 positivity score was based on the percentage of positive cells and on the intensity of nuclear expression; PD-L1 positivity was defined as CPS≥10; CD31 high-density had moderate to strong nuclear staining; and the CD4/CD8 ratio cut-off for positivity was &gt;0.2. Cox model was used to assess the correlation between BM and outcomes; PFS and OS were estimated by Kaplan-Meier method. Results: After screening of tumor tissues from 150 pts, a total of 111 were included in the final analysis (Table). In pts treated with VEGFR-TKI monotherapy, a significant correlation with PFS was observed with loss of PBRM1 expression (HR 0.58, p=0.035), PD-L1 negativity (HR 0.44, p=0.048), and high CD4/CD8 ratio (HR 0.62, p=0.073). CD31 density did not significantly correlate with PFS. A profile potentially predictive of angiogenesis (AP+) was defined based on the PBRM1 loss, PD-L1 negative, and high CD4/CD8. In pts treated with VEGFR-TKI monotherapy, tumors with the AP+ (43% of all cases) had a significantly longer median PFS (mPFS 23.8 vs. 11.8 months, p=0.003) and mOS (41.5 vs. 26.9 months, p=0.024) compared to the others. The AP+ retained its significant correlation with PFS (mPFS 23.8 vs. 11.1 months, p&lt;0.001) and OS (41.5 vs. 24.9, p=0.006) in pts receiving VEGFR-TKI-based therapies. The rate of AP+ tumors was 55.6% and 32.7% in pts with one or two IMDC risk factors, respectively (p=0.022). In the small cohort of pts treated with I/N, no differences were observed in PFS (p=0.64) and OS (p=0.75) between AP+ and AP-negative. Conclusions: The AP+ signature (loss of PBRM1, PD-L1 negative, and CD4/CD8 high ratio) was associated with improved clinical outcomes in mRCC pts at IMDC intermediate prognosis treated with VEGFR-TKI-based therapy; this correlation was significant regardless from the addition of IO to VEGFR-TKI monotherapy. Prospective validation of this signature is required for guiding the selection of the most appropriate 1L therapy. [Table: see text]